The detection of objects hidden behind articles is known. Suitable methods and/or devices can be used, for example, for finding valuable objects, in particular as so-called treasure-detecting devices. In addition, so-called line-locating devices or stud-locating devices are known. These have at least one sensor which can interact with the object to be found by means of at least one alternating voltage. The at least one sensor can be configured as inductive or capacitive. The article behind which the object is hidden can be, for example, a cladding in the form of wood and/or plasterboard whereby the object to be found is a support, for example, in the form of a beam. In such applications, sometimes weak signals occur. For the processing of such relatively weak signals, it is known to amplify them and/or to compensate them by means of regulation, wherein for a measurement evaluation, it is not the signal actually occurring at the sensor, but rather a control signal of the compensating regulation that is evaluated. The control signal can be an alternating voltage having a phase and an amplitude which can be generated by means of a pulse width modulator serving as a controlling element.
It is known to evaluate such a control signal in a phase space thereof. For example, from the earlier patent application DE 10 2013 226 887.4, an inductive sensor arrangement and a method for the detection of at least one target is known. It is provided that the target has a changeable shape or composition along a measuring direction and that in a 4-quadrant representation of the regulating signal, the angle of an imaginary vector to an x-axis of an xy-coordinate system which leads from the origin of the xy-coordinate system which corresponds to the regulated state of a transmitter-receiver coil system to a measurement point is a measure of the movement of the target in a measuring direction and/or the magnitude of the imaginary vector is a measure of a spacing of the target from the transmitter-receiver coil system normal to the measuring direction.
Furthermore, the earlier patent application DE 10 2014 010 671.3 relates to a method for determining at least one physical parameter by means of a sensor unit wherein the output signal of the sensor unit is substantially reduced to a fundamental wave of an excitation, wherein at least one pulse width modulation generates a respective correction signal with a variable pulse width and possibly variable phase and adds to an output signal of the sensor unit and thereby regulates the output signal in the whole phase space, wherein the pulse width of the correction signal and/or the phase of the correction signal is determined by the deviation of the output signal from zero.
DE 695 10 447 T2 discloses a device for recognizing the position of a stud in a partition wall.
In addition, from the international patent application WO 2012/104086 A2, a method for locating metallic or metal-containing objects and materials is known.
The patent application DE 10 2009 057 439 A1 concerns a device and a method for error-free capacitive measurement acquisition.